Laser light source, wavelength conversion light source, light combining light source, and projection system

ABSTRACT

A laser light source ( 300 ), a wavelength conversion light source, a light combining light source, and a projection system. The laser light source comprises a laser element array, a focusing optical element ( 33 ), a collimation optical element ( 34 ), an integrator rod ( 36 ) for receiving and homogenizing a secondary laser beam array ( 382 ), an angular distribution control element ( 35 ) disposed on the light path between the laser element array and the integrator rod ( 36 ) for enlarging the divergence angle of the laser beam array ( 382 ) in the direction of the short axis of the light distribution, such that the rate between the divergence angle of each of the secondary laser beam that enters the integrator rod ( 36 ) in the direction of the short axis of the light distribution and the divergence angle in the direction of the long axis is greater than or equal to 0.7.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to illumination and display technologies, and inparticular, it relates to a laser light source, a wavelength conversionlight source, a light combining light source, and a projection system.

2. Description of Related Art

With the advance of semiconductor technologies, the advantages of solidstate light sources are more and more evident. Laser light sources, as ahigh brightness and highly collimated new light source, are being morewidely used in projection and illumination fields. Laser light sourceshave small etendue, and can provide high brightness output light, butalso make it more difficult to homogenize the light.

FIG. 1 is a conventional laser light source that uses a square light rodto homogenize the light. Here, elements 11 a-11 c are laser diodes,elements 12 a-12 c are collimating lenses, element 13 is a converginglens, and element 14 is a square light rod. The collimating lenses 12a-12 c are an array of spherical or aspherical lenses, where each lenscorresponds to a laser diode. The laser light emitted by the laserdiodes 11 a-11 c is first collimated by the collimating lenses 12 a-12 cinto parallel light beams, and then converged by the converging lens 13to a small light spot; the light spot has a size that matches the sizeof the light entrance port of the square light rod 14. The square lightrod 14 is a hollow or solid light transmitting rod, to homogenize theinput light beam. However, empirical observation reveals that the lighthomogenizing effect of this system is not satisfactory, and the lightoutput from the output port of the light rod 14 still has separate laserlight spots and does not form a uniform surface distribution. Extendingthe length of the light rod 14 to increase the number of times ofreflections of the laser light inside the light rod does notsignificantly improve the light uniformity.

SUMMARY

An object of the present invention is to provide a laser light sourceswith improved uniformity of the output laser light beam.

An embodiment of the present invention provides a laser light source,which includes:

A laser light source array including a laser element array, forgenerating a collimated primary laser beam array;

A focusing optical element and a collimation optical element disposedsequentially after the laser light source array, wherein the collimatedprimary laser beam array sequentially passes through the focusingoptical element and the collimation optical element to form a collimatedsecondary laser beam array, wherein a distance between secondary laserbeams in the secondary laser beam array is smaller than a distancebetween primary laser beams in the primary laser beam array;

An integrator rod disposed after the collimation optical element, forreceiving and homogenizing the secondary laser beam array; and

An angular distribution control element disposed on an optical pathbetween the laser element array and the integrator rod, for enlarging adivergence angle of the laser beam array in a direction of a short axisof its light distribution, such that for each secondary laser beam ofthe secondary laser beam array that enters the integrator rod, a ratioof a divergence angle in a direction of a short axis of the lightdistribution to a divergence angle in a direction of a long axis isgreater than or equal to 0.7.

Preferably, the angular distribution control element is a collimatinglens array, each collimating lens corresponding to a laser element forcollimating a light emitted by the laser element;

Wherein the laser element is located on an optical axis of thecorresponding collimating lens and away from its focal point, andwherein for the primary laser beam output by the collimating lens, theratio of the divergence angle in the direction of the short axis of thelight distribution to the divergence angle in the direction of the longaxis is greater than or equal to 0.7.

Preferably, the angular distribution control element is at least onecylindrical lens, disposed between the collimation optical element andthe integrator rod, wherein each cylindrical lens corresponds to atleast one column of the secondary laser beams of the secondary laserbeam array outputted by the collimation optical element, wherein acolumn direction of each column of the at least one column of secondarylaser beams is parallel to a generating line of the cylindrical lens,and wherein for each secondary light beam of each column of secondarylight beams, its long axis of the light distribution is parallel to thegenerating line of the cylindrical lens;

Wherein for each secondary laser beam after its correspondingcylindrical lens, the ratio of the divergence angle in the direction ofthe short axis of the light distribution to the divergence angle in thedirection of the long axis is greater than or equal to 0.7.

Preferably, the angular distribution control element is a scatteringplate, disposed between the collimation optical element and theintegrator rod, wherein for the secondary laser beam array afterscattering by the scattering plate, the ratio of the divergence angle inthe direction of the short axis of the light distribution to thedivergence angle in the direction of the long axis is greater than orequal to 0.7.

Preferably, the angular distribution control element is a micro-lensarray, disposed between the collimation optical element and theintegrator rod, wherein each micro-lens in the micro-lens array is arectangle;

Wherein a direction of a short axis of a light distribution of thesecondary laser beam array incident on the micro-lens array is parallelto a long side of each micro-lens; and wherein for the secondary laserbeam array outputted from the micro-lens array, the ratio of thedivergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisis greater than or equal to 0.7.

Preferably, the laser light source array includes a laser element arrayand a collimating lens array, wherein each collimating lens correspondsto a laser element, for collimating the laser emitted by the laserelement, and wherein each laser element is located on an optical axis ofthe corresponding collimating lens and away from its focal point;

Wherein the angular distribution control element is located between thecollimation optical element and the integrator rod, for increasing thedivergence angle in the direction of the short axis of lightdistribution of each incident secondary laser beam, or decreasing thedivergence angle in the direction of the long axis of light distributionof each incident secondary laser beam, such that for each secondarylaser beam of the secondary laser beam array incident on the integratorrod, the ratio of the divergence angle in the direction of the shortaxis of the light distribution to the divergence angle in the directionof the long axis is greater than or equal to 0.7.

Preferably, the integrator rod is a solid rod, and wherein the angulardistribution control element and the integrator rod are formedintegrally as one body.

Another embodiment of the present invention provides a laser lightsource, including:

A laser light source array, for generating a collimated primary laserbeam array;

A focusing optical element and a collimation optical element disposedsequentially after the laser light source array, wherein the collimatedprimary laser beam array sequentially passes through the focusingoptical element and the collimation optical element to form a collimatedsecondary laser beam array, wherein a distance between secondary laserbeams in the secondary laser beam array is smaller than a distancebetween primary laser beams in the primary laser beam array;

An integrator rod disposed after the collimation optical element, forreceiving and homogenizing the secondary laser beam array, wherein alight entrance port of the integrator rod is larger in size than a lightexit port;

Wherein the light entrance port of the integrator rod has a first sideand a second side perpendicular to each other, the light exit port has afirst side and a second side perpendicular to each other, wherein thefirst side of the light entrance port and the first side of the lightexit port are parallel to each other, and wherein a length ratio of thefirst side of the light entrance port to the first side of the lightexit port is smaller than a length ratio of the second side of the lightentrance port to the second side of the light exit port;

Wherein when the secondary laser beam array enters the integrator rod,the direction of the long axis of the light distribution of eachsecondary laser beam is parallel to the first side of the light entranceport of the integrator rod.

Preferably, the first side of the light entrance port of the integratorrod is equal in length to the first side of the light exit port.

Preferably, the light entrance port of the integrator rod is a squareshape.

Preferably, an angular distribution control element is disposed on anoptical path between the laser element array and the integrator rod, forshaping the laser beam array, to increase the ratio of the divergenceangle in the direction of the short axis of the light distribution tothe divergence angle in the direction of the long axis for eachsecondary laser beam of the secondary laser beam array incident on theintegrator rod.

Another embodiment of the present invention provides a wavelengthconversion light source, including:

The above laser light source;

A wavelength conversion device, for receiving a light generated by thelaser light source and emitting a converted light.

Another embodiment of the present invention provides a light combininglight source, including:

the above laser light source;

A wavelength conversion light source, which includes an excitation lightsource and a wavelength conversion device, the wavelength conversiondevice receiving an excitation light generated by the excitation lightsource and emitting a converted light; and

A light combining device, where a light emitted by the laser lightsource and the converted light emitted by the wavelength conversionlight source are incident onto the light combining device from differentdirections and are combined by the light combining device into oneoutput light beam.

Another embodiment of the present invention provides a projectionsystem, including:

The above light combining light source;

A spatial light modulator device, for receiving the output light beamgenerated by the light combining light source and modulating it.

Compared to conventional technologies, embodiments of the presentinvention have the following advantages:

In embodiments of the present invention, the primary laser beam arraypasses through the focusing optical element and the collimation opticalelement and its cross-section is compressed to form the secondary laserbeam array, where the divergence angles of the secondary laser beams arelarger than the divergence angles of the primary laser beams. This way,the secondary laser beams can achieve a more uniform surfacedistribution after the downstream integrator rod. Meanwhile, an angulardistribution control element is provided on the optical path between thelaser element array and the integrator rod, to increase the divergenceangle in the direction of the short axis of the light distribution ofthe laser beam array, such that for each secondary laser beam in thesecondary laser beam array incident on the integrator rod, the ratio ofthe divergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisis greater than or equal to 0.7. This increases the number of times ofreflection inside the integrator rod for the light beams of thesecondary laser beam array in the direction of the short axis, so thatthe numbers of times of reflection inside the integrator rod for thelight beams in the direction of the short axis and for the light beamsin the direction of the long axis are closer to each other, whichfurther increases the uniformity of the secondary laser beam after theintegrator rod.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional laser light source which uses a squarelight rod for light homogenization.

FIG. 2 illustrates a working principle of a square light rod in theconventional technology.

FIG. 3A schematically illustrates the structure of a laser light sourceaccording to an embodiment of the present invention.

FIG. 3B schematically illustrates the light emitted by a laser element.

FIG. 3C schematically illustrates the light emitted by the laser elementafter a collimating lens.

FIG. 3D schematically illustrates the structure of a micro-lens array inthe laser light source according to an embodiment of the presentinvention.

FIG. 4 schematically illustrates the situations when the laser elementis located at or off the focal point of the collimating lens.

FIG. 5 schematically illustrates the structure of a laser light sourceaccording to another embodiment of the present invention.

FIG. 6 is a perspective view of the integrator rod of the laser lightsource of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The inventors of the present invention studied the problems ofnon-uniformity of the output light from the laser light source of FIG.1, and discovered that, a key factor for a typical light beam to behomogenized by the light rod is that the angular distribution of thelight beam is continuous. In such situations, after the light isreflected multiple times in the light rod, the surface distribution ofthe light is continuous; the more time the light is reflected, thebetter the uniformity of its surface distribution.

However, the laser beam that is converged by the converging lens 13 isdifferent from a typical light beam in that it is formed of multiplelaser beams, and each laser beam is generated by a laser diode and itscorresponding collimating lens; as a result, the angular distribution ofthe overall light beam is not continuous, but is discrete. Thepropagation of these discrete laser beams in the light rod 14 is shownin FIG. 2. The laser beam L1 enters with an incident angle α, and exitswith an exit angle α; the laser beam L2 enters with an incident angle β,and exits with an exit angle β. Because the divergence angle of eachlight beam is small, after multiple reflections inside the light rod,each of them remains a thin light beam, and as a result, at the exitport of the light rod, they cannot have a mixing effect to generate auniform light distribution.

Embodiments of the present invention are described below with referenceto the drawings.

First Embodiment

FIG. 3A schematically illustrates the structure of a laser light sourceaccording to an embodiment of the present invention. The laser lightsource 300 includes a laser light source array, which generates an arrayof collimated primary laser beams 381. The laser light source arrayincludes a laser element array and a collimating lens array. The laserelement array includes laser elements 31 a, 31 b and 31 c, and thecollimating lens array includes 32 a, 32 b and 32 c, where eachcollimating lens corresponds to a laser element. The light emittinglocation of the laser element is located at the focal point of thecorresponding collimating lens, so the light emitted by the laserelement is collimated by the collimating lens.

In this embodiment, the laser elements are laser diodes, or otherelements that generate laser light, without limitation. Of course, thenumber of elements in the laser element array and the collimating lensarray are only examples and do not limit the invention.

Refer to FIG. 3B, which schematically illustrates the light emitted by alaser element. The light emitting surface of the laser element 31 is arectangular shape; the divergence angle of the light in a cross-sectionthat passes through the long side 311 of the rectangle is α, and thedivergence angle of the light in a cross-section that passes through theshort side 312 of the rectangle is β, where α is smaller than β.Typically, β is greater than five times α. I.e., the long axis 313 ofthe output light distribution of the laser element 31 is parallel to theshort side 312 of the rectangle, and the short axis 314 of the outputlight distribution is parallel to the long side 311 of the rectangle.

The primary laser beam which is emitted by the laser element 31 andcollimated by the collimating lens is not a strict parallel beam.Compared to the light emitted by the laser element, the collimated laserbeam has a smaller divergence angle, but the collimated laser beam stillhas a long axis and a short axis in its light distribution. Refer toFIG. 3C, which schematically illustrates the light emitted by the laserelement 31 after the collimating lens 32. It should be noted that thelong axis 315 of the light distribution of the primary laser beam isparallel to the long side 311 of the light emitting surface of the laserelement 31, and the short axis 316 of the light distribution of theprimary laser beam is parallel to the short side 312 of the lightemitting surface of the laser element 31; the ratio of the divergenceangle in the direction of the long axis 315 to that in the direction ofthe short axis 316 is relatively large, typically greater than 5. Forclarity, in the following descriptions, the “long axis direction” and“short axis direction” refer to the long axis direction and the shortaxis direction of the light distribution of the light beam.

This way, of the primary laser beam array 381 generated by the laserelements and collimated by the collimating lenses, the optical axes ofthe primary laser beams are parallel to each other, and each laser beamhas a certain divergence angle, and the ratio of the divergence angle inthe direction of the long axis of the light distribution to that in thedirection of the short axis is still relatively large.

The laser light source 300 further includes a focusing optical element33 and a collimation optical element 34 disposed sequentially after thelaser light source array, where the primary laser beam array 381sequentially passes through the focusing optical element 33 and thecollimation optical element 34 to form a collimated secondary laser beamarray 382.

In this embodiment, the focusing optical element is a convex lens 33 andthe collimation optical element is a concave lens 34. The convex lens 33and the concave lens 34 are confocal, where the focal point of theconcave lens 34 is a virtual focal point, which is located on theoptical path after the concave lens 34. This way, the primary laser beamarray 381 is first focused by the convex lens 33 and converges towardits focal point, and the cross-sectional size of the beam incident onthe concave lens 34 is smaller than the cross-sectional size of the beamincident on the convex lens 33. Because these laser beams are alsoconverging toward the focal point of the concave lens, the light beamsafter the concave lens 34 are again parallel, forming the collimatedsecondary laser beam array 382; but the cross-sectional size of thelaser beams is compressed, i.e., the distance between the secondarylaser beams in the secondary laser beam array 382 is smaller than thedistance between the primary laser beams in the primary laser beamarray.

Based on the principle of the conservation of etendue, when thecross-sectional size of a light beam is compressed, its divergence anglewill increase, i.e.,

S ₁*sin² θ₁ =S ₂*sin² θ₂   (1)

where S₁, θ₁ are respectively the cross-sectional size and divergencehalf-angle of the primary laser beam array, and S₂, θ₂ are respectivelythe cross-sectional size and divergence half-angle of the secondarylaser beam array. Here, S₂<S₁, so θ₂ is greater than θ₁. It should benoted that in equation (1), the divergence half-angle is not the anglebetween the laser beams, but a half of the divergence angle of eachlaser beam itself.

In practice, by controlling the positions and curvatures of the convexlens 33 and the concave lens 34, the compression ratio of thecross-sectional size of the secondary laser beam array 382 to that ofthe primary laser beam array 381 can be controlled (the compressionratio of the light beams is approximately the ratio of the focaldistances of the convex lens 33 and the concave lens 34). This in turncontrols the rate of increase of the divergence half-angle of each laserbeam in the secondary laser beam array relative to the divergencehalf-angle of each laser beam in the primary laser beam array. It shouldbe understood that, for each laser beam in the secondary laser beamarray, the rate of increase of the divergence angle in the direction ofthe long axis of light distribution is the same as that in the directionof the short axis, so the ratio of the divergence angles in the twodirections are still relatively large.

The laser light source 300 further includes an angular distributioncontrol element 35 disposed after the collimation optical element 34,for receiving the secondary laser beam array 382 and shaping it, so thatfor each secondary laser beam of the secondary laser beam array 382after the shaping, the ratio of the divergence angle in the direction ofthe short axis of the light distribution to the divergence angle in thedirection of the long axis is greater than or equal to 0.7.

Specifically, in this embodiment, the angular distribution controlelement 35 is a cylindrical lens. Because a cylindrical lens can onlychange the divergence angle of a light beam in one dimension, it can beused to increase the divergence angle of the laser beam in the directionof the short axis without changing the divergence angle in the directionof the long axis. The curvature of the cylindrical surface of thecylindrical lens can be designed to so that the ratio of the divergenceangle for each laser beam in the direction of the short axis to thedivergence angle in the direction of the long axis is greater than orequal to 0.7. To achieve the above goal, the long axis of the lightdistribution of each secondary laser beam of the secondary laser beamarray that are incident on the cylindrical lens is parallel to thegenerating line of the cylindrical lens surface.

The laser light source 300 further includes an integrator rod 36disposed after the angular distribution control element 35, forreceiving and homogenizing the secondary laser beam array that has beenshaped by the angular distribution control element 35.

Based on current understanding of integrator rods (the square light roddiscussed in the background section and cone shaped light rods are bothexamples of integrator rods), the incident light should enter theintegrator rods with a relatively large angular range in order toproduce a good light homogenization effect, because only in suchsituations the light beams can be reflected multiple times inside theintegrator rod to be homogenized. However, through study the inventorsof the instant invention gained deeper understanding of integrator rods,i.e., when applied in laser field, merely converging multiple laserbeams to form an large angular range of input light does not work;rather, the divergence half-angle of each laser beam must be increased.As long as the divergence half-angle of each laser beam is sufficientlyincreased, even when the multiple laser beams are near parallel to eachother, good homogenization effect can be achieved by the integrator rod.

However, when increasing the divergence half-angle of each laser beam,the rates of increase of the divergence angle for each laser beam in thedirection of the long axis and in the direction of the short axis of thelight distribution are approximately equal; thus, when entering theintegrator rod, even though the divergence half-angle of each laser beamis increased, the divergence angle of each laser beam in the directionof the short axis is much smaller than the divergence angle in thedirection of the long axis, so the number of reflections of the lightbeam inside the integrator rod for these two directions are alsosignificantly different; as a result, the light spot formed by eachsecondary laser beam on the plane at the exit port of the integrator rodis mixed relatively uniformly in the direction of the long axis, whilethe uniformity in the direction of the short axis is relatively poor.Therefore, in this embodiment, by providing the angular distributioncontrol element between the collimation optical element and theintegrator rod, for each secondary laser beam entering the integratorrod, the ratio of the divergence angle in the direction of the shortaxis to the divergence angle in the direction of the long axis of thelight distribution is greater than or equal to 0.7, so that the lighthomogenizing effect of each secondary laser beam in the direction of theshort axis is improved.

In this embodiment, the angular distribution control element may also bea cylindrical lens array. The cylindrical lens array is arranged suchthat each cylindrical lens corresponds to at least one column ofsecondary laser beams, and the column direction of each such column ofsecondary laser beams is parallel to the generating line of thecylindrical lens. Further, in the at least one column of secondary lightbeams, the long axes of the light distribution of the secondary lightbeams are parallel to each other and parallel to the generating line ofthe cylindrical lens. Compared to using only one cylindrical lens, usinga cylindrical lens array can increase the divergence angle in thedirection of the short axis of the light distribution of each secondarylaser beam by a larger amount, so that it is closer to the divergenceangle in the direction of the long axis. However, using only onecylindrical lens is more convenient in fabrication.

In this embodiment, when the laser beams emitted by the laser elementsthemselves are already well collimated, the collimating lenses may beomitted. However, it should be noted that when the collimating lensarray is omitted form the laser light source array, the directions ofthe long axis and short axis of each primary laser beam in the primarylaser beam array are rotated by 90 degrees. Therefore, correspondingly,as compared to the above described embodiment, the positioning of thecylindrical lens should be rotated by 90 degrees in the planeperpendicular to the optical axis of the laser beam array.

Of course, in this embodiment, the angular distribution control element35 does not have to be a cylindrical lens array; it may be a scatteringplate, where the scattering plate scatters the secondary laser beam tolarger angles in the direction of the short axis of the secondary laserbeam than in the direction of the long axis, or it only scatters thesecondary laser beam in the direction of the short axis, such that theratio of the divergence angle in the direction of the short axis of thelight distribution of the laser beam to the divergence angle in thedirection of the long axis is greater than or equal to 0.7.

For example, the scattering structure on the surface of the scatteringplate contains multiple closely packed micro-structures that aretranslucent, where each micro-structure is a cylindrical shape; further,the generating lines of the micro-structures are parallel to each otherand are parallel to the direction of the long axis of the lightdistribution of the incident secondary laser beams. Or, translucentscattering structures shaped like cylinders or parts of cylinders may bemixed in a transparent substrate, where the scattering structures andthe substrate have different refractive indices; further, the generatinglines of the scattering structures are parallel or near parallel to eachother and are parallel to the direction of the long axis of the lightdistribution of the incident secondary laser beams. Or, the scatteringplate may be a diffraction optical element (DOE); by designing the phaseof each point of the DOE, the DOE only increases the divergence angle inthe direction of the short axis of the light distribution of theincident secondary laser beam, or increase the divergence angle in thedirection of the short axis of the light distribution of the incidentsecondary laser beam more than in the direction of the long axis.

In this embodiment, the angular distribution control element 35 may alsobe a micro-lens array, formed by joining together multiple rectangularlenses. Refer to FIG. 3D, which schematically illustrates the structureof a micro-lens array in the laser light source according to thisembodiment. Each micro-lens 351 is a rectangle, the lengths of its twosides being D₁ and D₂ respectively, where D₁ is smaller than D₂. When aparallel light beam is incident on the micro-lens array, it forms alight beam having different divergence angles along the two sides of therectangle, where the ratio of the divergence angle along the long sideto that along the short side is approximately D₂:D₁. Therefore, for eachsecondary laser beam in the secondary laser beam array incident on themicro-lens array, the short axis of the light distribution may be madeparallel to the long side of the micro-lenses, so that the increase ofthe divergence angle in the direction of the short axis of the lightdistribution of each secondary laser beam is more than that in thedirection of the long axis. By designing the ratio of the two sides ofthe micro-lenses and the surface curvatures of the micro-lenses, theratio of the divergence angle in the direction of the short axis of thelight distribution of the output secondary laser beams from themicro-lens array to the divergence angle in the direction of the longaxis is greater than or equal to 0.7.

In this embodiment, the angular distribution control element and theintegrator rod may be formed integrally as one body. For example, theintegrator rod may be a solid rod, and its entrance port may be formedinto a cylindrical structure, or the entrance port may be provided witha scattering structure like the scattering plate.

In the above embodiment, the angular distribution control element 35 islocated between the collimation optical element and the integrator rod.In practice, the angular distribution control element 35 may be locatedanywhere on the optical path between the laser light source array andthe integrator rod; as long as for each laser beam of the laser beamarray emitted by the laser light source array, the ratio of thedivergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisis made greater than or equal to 0.7, the object of the presentinvention is achieved. In this embodiment, the collimation opticalelement is a concave lens. In practice, the collimation optical elementmay also be a convex lens; as long as the focusing optical element 33and that convex lens are confocal, the effect is the same as using aconcave lens, except that the length of the system in the lightpropagation direction will increase, and the overall system will becomeslightly larger. More generally, the focusing optical element and thecollimation optical element are not limited to the convex lens orconcave lens in this embodiment; for example, the focusing opticalelement may use one or more reflecting mirrors to focus the multiplelaser beams, and the collimation optical element may be a Fresnel lens;any suitable optical elements that can achieve the above-describedfunctions are within the scope of this invention.

Second Embodiment

In the first embodiment, by providing an angular distribution controlelement between the laser light source array and the integrator rod, theratio of the divergence angle in the direction of the short axis of eachlaser beam to the divergence angle in the direction of the long axis isincreased. However, this can be achieved not by providing the angulardistribution control element between the laser light source array andthe integrator rod, but by using the collimating lens array of the laserlight source array. In this embodiment, the collimating lens arrayfunctions as the angular distribution control element.

For clarity, the “aspect ratio” below refers to the ratio of the longaxis to the short axis of an ellipse. Refer to FIG. 4, when the laserelement 41 is located right at the focal point of the collimating lens42, the collimating lens 42 is located at position A on the optical axisof the laser element, and the output laser beam of the collimating lens42 is focused by a focusing lens (not shown in the figure) to form alight spot on the target plane which is a long and narrow ellipse a.When the laser element 41 is located on the optical axis of thecollimating lens 42 but away from its focal point, for example when thecollimating lens 42 located at position B which is closer to the laserelement 41, the output laser beam of the collimating lens 42 is focusedby the focusing lens to form a light spot on the target plane which isan ellipse b, where the aspect ratio of the ellipse b is smaller thanthe aspect ratio of the ellipse a. If the collimating lens 42 is locatedat a position A which is even closer to the laser element 41, the outputlaser beam of the collimating lens 42 is focused by the focusing lens toform a light spot on the target plane which is an ellipse c, where theaspect ratio of the ellipse c is smaller than the aspect ratio of theellipse b.

Based on experiments and theoretical analyses, the inventors of thepresent invention discovered that: in the off-focus situation, for thelight emitted by the laser element, the distance between the outer-mostlight in the direction of the long axis of the light distribution andthe optical axis of the collimating lens increases faster by a few timesthan the distance between the outer-most light in the direction of theshort axis and the optical axis. From FIG. 3B, it can be seen that thelong axis of the light distribution of the light emitted by the laserelement is parallel to the short side of the light emitting surface ofthe laser element, and the short axis of the light distribution isparallel to the long side of the light emitting surface of the laserelement. Thus, in the light beam output from the collimating lens, thedivergence angle in the direction parallel to the short side of thelight emitting surface of the laser element increases much faster thanthe divergence angle in the direction parallel to the long side of thelight emitting surface of the laser element.

From FIG. 3C, it can be seen that in the light beam outputted by thecollimating lens, the direction parallel to the short side of the lightemitting surface of the laser element is the direction of the short axisof the light distribution of the light beam, and the direction parallelto the long side of the light emitting surface of the laser element isthe direction of the long axis of the light distribution of the lightbeam. Therefore, in the output light beam of the collimating lens, thedivergence angle in the direction of the short axis of the lightdistribution increases faster by a few times than the divergence anglein the direction of the long axis. As a result, the short axis of theelliptical light spot on the target plane increases faster than the longaxis, causing the aspect ratio of the elliptical light spot to change.

Thus, different from the first embodiment, in this embodiment, eachlaser element is located on the optical axis of the correspondingcollimating lens but away from its focal point (referred to as off-focusbelow), and the degree of off-focus is such that for each primary laserbeam output by the collimating lens, the ratio of the divergence anglein the direction of the short axis of the light distribution to thedivergence angle in the direction of the long axis is greater than orequal to 0.7.

In the first embodiment, the scattering plate or the cylindrical lens,in particular the scattering plate, will cause some light loss. In thisembodiment, by using the off-focus technique, the light loss is reducedand the efficiency is higher.

Preferably, the collimating lens is moved from the ideal position (i.e.the position where the laser element is located at the focal point ofthe collimating lens) toward the laser element, i.e., to make thedistance between the laser element and the corresponding collimatinglens less than the focal distance of the collimating lens; as a resultthe light collecting angle of the collimating lens is larger, and thelight utilization efficiency is higher. The amount of off-focus shouldnot be too large, to avoid too large a divergence angle of the outputlight beam of the collimating lens. Preferably, the distance between theposition of the off-focus collimating lens and its ideal position isless than or equal to 0.05 mm.

In practice, the techniques of the first and second embodiments may becombined. I.e., in the laser light source array, each laser element isoff-focus with respect to its corresponding collimating lens, and at thesame time, an angular distribution control element is provided betweenthe laser light source array and the integrator rod, so that for eachlaser beam that enters the integrator rod, the ratio of the divergenceangle in the direction of the short axis of the light distribution tothe divergence angle in the direction of the long axis is greater thanor equal to 0.7.

Third Embodiment

In the above embodiments, the purpose of the invention is achieved byshaping the laser beams on the optical path before reaching theintegrator rod. Alternatively, by designing the integrator rod, uniformlight homogenization in two directions can be achieved by the integratorrod even for light beams where the ratio of the divergence angle in thedirection of the short axis to that in the direction of the long axis isrelatively small. This is explained below.

Refer to FIG. 5, which schematically illustrates the structure of alaser light source according to another embodiment of the presentinvention. The laser light source 500 includes a laser light sourcearray, a focusing optical element 53, a collimation optical element 54and an integrator rod 56.

Differences between this embodiment and the earlier-describedembodiments include:

In this embodiment, the laser light source array includes a laserelement array 51 and a collimating lens array 52 which correspondone-to-one with each other, for generating a collimated primary laserbeam array. The laser elements and the corresponding collimating lensesare not off-focus. Of course, when the laser beams emitted by the laserelements themselves are well collimated, the collimating lens array maybe omitted.

The primary laser beam array is sequentially focused by the focusingoptical element 53 and collimated by the collimation optical element 54to form a secondary laser beam array, which is directly incident ontothe integrator rod 56.

Refer to FIG. 6, which is a perspective view of the integrator rod ofthe laser light source of FIG. 5. The light entrance port 561 of theintegrator rod 56 is larger in size than the light exit port 562. Inthis embodiment, the light entrance port 561 and the light exit port 562are both rectangles. Preferably, the ratio of the long side to the shortside of the light exit port 562 is 16/9 or 4/3, to match the shape ofthe light valve of the light modulating device in the downstream opticalpath.

In this embodiment, the long side 561 a of the light entrance port 561is the first side, and the short side 561 b is the second side. The longside 562 a of the light exit port 562 is the first side, and the shortside 562 b is the second side. The long side 561 a of the light entranceport is parallel to the long side 562 a of the light exit port, and thelength ratio of the first side 561 a of the light entrance port to thefirst side 562 a of the light exit port is smaller than the length ratioof the second side 561 b of the light entrance port to the second side562 b of the light exit port.

When the secondary laser beam array is incident on the light entranceport 561 of the integrator rod 56, the direction of the long axis ofeach secondary laser beam is parallel to the first side 561 a of thelight entrance port 561; hence, the direction of the short axis of eachsecondary laser beam is parallel or near parallel to the short side 561b of the light entrance port 561. Because the length ratio of the firstside 561 a of the light entrance port to the first side 562 a of thelight exit port is smaller than the length ratio of the second side 561b of the light entrance port to the second side 562 b of the light exitport, the light beams in the direction of the short axis of the laserbeam are reflected more times inside the integrator rod than the lightbeams in the direction of the long axis. This improves the uniformity inthe direction of the short axis of the secondary laser beam array afterthe light homogenization rod.

In this embodiment, the length ratio of the long side 561 a of the lightentrance port of the integrator rod to the long side 562 a of the lightexit port is preferably 1, to avoid increasing the divergence angle inthe direction of the long axis of the light distribution of thesecondary laser beams.

Preferably, the light entrance port 561 of the integrator rod is asquare shape, so as to couple more secondary laser beams into theintegrator rod.

In this embodiment, the angular distribution control element of thefirst embodiment and/or the off-focus technique of the secondembodiments may be additionally used, to increase the ratio of thedivergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisfor each secondary laser beam of the secondary laser beam array thatenters on the integrator rod. This in turn improves the uniformity ofthe laser beams after the integrator rod. It should be understood that,when using the integrator rod of this embodiment, if the angulardistribution control element and/or the off-focus technique are alsoused to increase the ratio of the divergence angle in the direction ofthe short axis of the light distribution of the laser beam to thedivergence angle in the direction of the long axis, the requirement onthe ratio can be less strict than in the cases of the first and secondembodiments;

here the ratio may be less than 0.7, so long as it is larger than thecorresponding ratio for the secondary laser beams of the secondary laserbeam array entering the integrator rod when not using the angulardistribution control element and/or the off-focus technique.

The various embodiments in this disclosure are described in aprogressive manner, where each embodiment is described by emphasizingits differences from other embodiments. The common or similar featuresof the embodiments can be understood by referring to each other.

Another embodiment of the present invention provides a wavelengthconversion light source, including a laser light source which may havethe structures and functions of the laser light source described in theabove embodiments, and a wavelength conversion device which receives thelight generated by the laser light source and emits a converted light.

Another embodiment of the present invention provides a light combininglight source, including a laser light source which may have thestructures and functions of the laser light source described in theabove embodiments, and a wavelength conversion light source. Thewavelength conversion light source includes an excitation light sourceand a wavelength conversion device, which receives the excitation lightgenerated by the excitation light source and emits a converted light.The light combining light source further includes a light combiningdevice, where the light emitted by the laser light source and theconverted light emitted by the wavelength conversion light source areincident onto the light combining device from different directions andare combined by the light combining device into one light beam to beoutput.

Another embodiment of the present invention provides a projectionsystem, including the above light combining light source, and furtherincluding a spatial light modulator device, for receiving the light beamfrom the light combining light source and modulating it. The projectionsystem may employ various projection technologies, such as liquidcrystal display (LCD) projection technology, digital light processor(DLP) projection technology, etc. The above light combining light sourcecan also be used in illumination systems, such as stage lighting.

The above descriptions disclose the embodiments of the presentinvention, but do not limit the scope of the invention. Thus, it isintended that the present invention cover modifications and variationsthat come within the scope of the appended claims and their equivalents,as well as direct or indirect applications of the embodiments in otherrelated technical fields.

1. A laser light source, comprising: a laser light source arrayincluding a laser element array, for generating a collimated primarylaser beam array; a focusing optical element and a collimation opticalelement disposed sequentially after the laser light source array,wherein the collimated primary laser beam array sequentially passesthrough the focusing optical element and the collimation optical elementto form a collimated secondary laser beam array, wherein a distancebetween secondary laser beams in the secondary laser beam array issmaller than a distance between primary laser beams in the primary laserbeam array; an integrator rod disposed after the collimation opticalelement, for receiving and homogenizing the secondary laser beam array;and an angular distribution control element disposed on an optical pathbetween the laser element array and the integrator rod, for enlarging adivergence angle of the secondary laser beam array in a direction of ashort axis of its light distribution, such that for each secondary laserbeam of the secondary laser beam array that enters the integrator rod, aratio of a divergence angle in a direction of a short axis of the lightdistribution to a divergence angle in a direction of a long axis isgreater than or equal to 0.7.
 2. The laser light source of claim 1,wherein the angular distribution control element is a collimating lensarray, each collimating lens corresponding to a laser element forcollimating a light emitted by the laser element; and wherein the laserelement is located on an optical axis of the corresponding collimatinglens and away from its focal point, and wherein for the primary laserbeam output by the collimating lens, the ratio of the divergence anglein the direction of the short axis of the light distribution to thedivergence angle in the direction of the long axis is greater than orequal to 0.7.
 3. The laser light source of claim 1, wherein the angulardistribution control element is at least one cylindrical lens, disposedbetween the collimation optical element and the integrator rod, whereineach cylindrical lens corresponds to at least one column of thesecondary laser beams of the secondary laser beam array outputted by thecollimation optical element, wherein a column direction of each columnof the at least one column of secondary laser beams is parallel to agenerating line of the cylindrical lens, and wherein for each secondarylight beam of each column of secondary light beams, its long axis of thelight distribution is parallel to the generating line of the cylindricallens; and wherein for each secondary laser beam after its correspondingcylindrical lens, the ratio of the divergence angle in the direction ofthe short axis of the light distribution to the divergence angle in thedirection of the long axis is greater than or equal to 0.7.
 4. The laserlight source of claim 1, wherein the angular distribution controlelement is a scattering plate, disposed between the collimation opticalelement and the integrator rod, wherein for the secondary laser beamarray after scattering by the scattering plate, the ratio of thedivergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisis greater than or equal to 0.7.
 5. The laser light source of claim 1,wherein the angular distribution control element is a micro-lens array,disposed between the collimation optical element and the integrator rod,wherein each micro-lens in the micro-lens array is a rectangle; whereina direction of a short axis of a light distribution of the secondarylaser beam array incident on the micro-lens array is parallel to a longside of each micro-lens; and wherein for the secondary laser beam arrayoutputted from the micro-lens array, the ratio of the divergence anglein the direction of the short axis of the light distribution to thedivergence angle in the direction of the long axis is greater than orequal to 0.7.
 6. The laser light source of claim 1, wherein the laserlight source array includes a laser element array and a collimating lensarray, wherein each collimating lens corresponds to a laser element, forcollimating the laser emitted by the laser element, and wherein eachlaser element is located on an optical axis of the correspondingcollimating lens and away from its focal point; wherein the angulardistribution control element is located between the collimation opticalelement and the integrator rod, for increasing the divergence angle inthe direction of the short axis of light distribution of each incidentsecondary laser beam, or decreasing the divergence angle in thedirection of the long axis of light distribution of each incidentsecondary laser beam, such that for each secondary laser beam of thesecondary laser beam array incident on the integrator rod, the ratio ofthe divergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisis greater than or equal to 0.7.
 7. The laser light source of claim 1,wherein the integrator rod is a solid rod, and wherein the angulardistribution control element and the integrator rod are formedintegrally as one body.
 8. A laser light source, comprising: a laserlight source array, for generating a collimated primary laser beamarray; a focusing optical element and a collimation optical elementdisposed sequentially after the laser light source array, wherein thecollimated primary laser beam array sequentially passes through thefocusing optical element and the collimation optical element to form acollimated secondary laser beam array, wherein a distance betweensecondary laser beams in the secondary laser beam array is smaller thana distance between primary laser beams in the primary laser beam array;an integrator rod disposed after the collimation optical element, forreceiving and homogenizing the secondary laser beam array, wherein alight entrance port of the integrator rod is larger in size than a lightexit port; wherein the light entrance port of the integrator rod has afirst side and a second side perpendicular to each other, the light exitport has a first side and a second side perpendicular to each other,wherein the first side of the light entrance port and the first side ofthe light exit port are parallel to each other, and wherein a lengthratio of the first side of the light entrance port to the first side ofthe light exit port is smaller than a length ratio of the second side ofthe light entrance port to the second side of the light exit port; andwherein when the secondary laser beam array enters the integrator rod,the direction of the long axis of the light distribution of eachsecondary laser beam is parallel to the first side of the light entranceport of the integrator rod.
 9. The laser light source of claim 8,wherein the first side of the light entrance port of the integrator rodis equal in length to the first side of the light exit port.
 10. Thelaser light source of claim 8, wherein the light entrance port of theintegrator rod is a square shape.
 11. The laser light source of claim 8,further comprising an angular distribution control element disposed onan optical path between the laser element array and the integrator rod,for shaping the secondary laser beam array, to increase the ratio of thedivergence angle in the direction of the short axis of the lightdistribution to the divergence angle in the direction of the long axisfor each secondary laser beam of the secondary laser beam array incidenton the integrator rod.
 12. A wavelength conversion light source,comprising: the laser light source of claim 1; and a wavelengthconversion device, for receiving a light generated by the laser lightsource and emitting a converted light.
 13. A light combining lightsource, comprising: the laser light source of claim 1; a wavelengthconversion light source, which includes an excitation light source and awavelength conversion device, the wavelength conversion device receivingan excitation light generated by the excitation light source andemitting a converted light; and a light combining device, where a lightemitted by the laser light source and the converted light emitted by thewavelength conversion light source are incident onto the light combiningdevice from different directions and are combined by the light combiningdevice into one output light beam.
 14. A projection system, comprising:the light combining light source of claim 13; and a spatial lightmodulator device, for receiving the output light beam generated by thelight combining light source and modulating it.